1. Field of the Invention
The present invention concerns an inflatable tubular sleeve for tubing or obturating a well or a pipe.
2. Background Information
Flexible tubular preforms that can be hardened in situ have already been proposed for tubing an oil drilling well and for similar applications; they are adapted to be put in place in a radially folded or non-expanded state--in which state they have a small overall size in the radial direction--and then unfolded and/or expanded radially by application of internal pressure before being hardened in situ, for example by polymerization.
Preforms of this type are described in documents WO-91/18180, WO-94/21887 and WO-94/25655, for example.
The expression "radially deformable" is used to refer to sleeves that can be radially deployed by simple unfolding (as is the case with the preform described in WO-91/18180, for example) or that can simply be expanded radially (without unfolding) by increasing their diameter due to the effect of internal pressure or that can be successively unfolded and then expanded (as is the case with the matrix and the preform of document WO-94/25655, for example).
The invention has been conceived as a sleeve used as a tool for expanding a preform, this tool being of the same general type as the preform expander tool--called a matrix--described in WO-94/25655, cited above; this matrix is initially attached to the preform, being mounted inside the latter. After inflation of the matrix/preform combination and solidification of the preform the matrix is pulled out.
However, the invention applies equally to sleeves used as tools for obturating the wall of a well, to prevent fluid leaks, this tool being commonly known in the art as a "packer".
In one possible embodiment, the tubular sleeve that is the subject matter of the invention can also consist in the preform itself.
During the operation of radial deformation (by unfolding and/or expansion) of a sleeve of the above kind within a well or a pipe, if the expansion of the preform is not controlled there is a risk of pockets of liquid forming that are trapped between the sleeve and the wall of the well or the pipe. In oil drilling and like applications it is common for the well or the pipe to be filled with water, mud or some other liquid.
This is obviously a problem, since the sleeve or the preform surrounding it cannot be pressed correctly against the wall of the well or the pipe and the tubing obtained is not perfectly cylindrical and is not firmly anchored.
An attempt has been made to overcome this difficulty in the case of inflatable membranes equipping obturating tools (packers) by varying the composition of the material of the membrane--or sleeve--(based on synthetic rubber) from one end to the other, so that its resistance to radial expansion varies progressively. Accordingly, when a fluid under pressure is introduced into the tool the membrane expands progressively from one end of the tool to the other, expelling in a regular manner the liquid trapped between the membrane and the well or the pipe as expansion proceeds, towards the end at which the resistance to expansion is highest, i.e. the end at which expansion occurs last.
Although in theory this technique is satisfactory, it is difficult and costly to implement because the composition of the material of the sleeve is not the same throughout the product, the variation in its composition is difficult to control and, most importantly, it cannot be applied to long sleeves.
For this reason the objective of the present invention is to propose a sleeve of the kind just mentioned adapted to be used for tubing a well or a pipe, in particular for oil industry applications, the sleeve having a structure such that it also expands progressively from one end to the other, in a manner that is totally controlled and independently of its length.
In accordance with the invention, this result is achieved by the virtue of the fact that the wall of the sleeve is provided with a series of identical breakable restraining rings offset axially relative to each other and adapted to break one after the other in the longitudinal direction of the sleeve when the latter is inflated by an internal fluid under pressure.